This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Glutamate is the predominant excitatory transmitter in the central nervous system, and glutamate homeostasis involves the interaction of multiple membrane transporters that are responsible for its packaging into synaptic vesicles (VGLUTs 1-3), its reuptake into glia and neurons (EAATs 1-5), the transfer of its precursor, glutamine, between glia and neurons (presumably involving transport systems A, N, and/or ASC) and its export from glial cells (System Xc;Sxc). There are fundamental unanswered questions concerning many details of this complex system of interacting transport systems. These range from the mechanisms of glutamate and glutamine transport to the roles that each transporter subtype plays in influencing the spatiotemporal profile of synaptically released glutamate and ultimately signaling in the brain. This subproject proposes to organize a multidisciplinary approach involving a team of investigators with expertise in synthetic chemistry, computational modeling, biochemistry, photophysics, and molecular physiology in order to comprehensively address these questions. The specific aims are: 1. To elucidate the molecular pharmacology of the EAAT, VGLUT, Sxc and glutamine transport systems by identifying and characterizing the structural determinants involved in substrate selectivity and pore access in order to develop novel selective inhibitors. 2. To characterize the structural mechanisms of the transporters and test the novel pharmacophore model-derived compounds. 3. To characterize the roles of various transporters in physiological (hippocampal inhibitory and excitatory synaptic transmission) and pathophysiological (hippocampal excitotoxicity) processes.